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Successful Metallurgical Program for the Montagne d'Or Gold Project

SRK News | Issue 53: Metallurgy and Mineral Processing

A4   |   Letter

During 2016, SRK undertook a feasibility-level development program to describe the metallurgical process for Nordgold’s Montagne d’Or gold project located in French Guiana. The objective was to develop a practical process flowsheet and define the process operating parameters and metal recoveries in sufficient detail and to the required level of accuracy. This included developing a process design criteria, equipment requirements, process capital costs and operating costs. This program involved numerous stakeholders, professionals and organisations that all contributed to a successful outcome. The following points were instrumental in the program’s success:

• Holding a kick-off meeting with all stakeholders and disciplines to ensure that the scope of the program and expected outcomes are fully defined.

• Involving experienced project geologists and mining engineers in the selection of drill core intervals from which both master composites and variability composites could be developed for the metallurgical program. For the Montagne d’Or project, three master composites were selected to represent three major ore zones. In addition, twenty-two variability composites were developed to represent different ore lithologies, grade ranges and mining phases. Also, comminution composites representing each of the ore and waste lithologies were developed from core.

• Selecting qualified and experienced metallurgical laboratories to undertake the defined scope of work according to the defined schedule requirements. Several different commercial metallurgical laboratories specialising in comminution, cyanidation, gravity concentration, solid liquid separation, carbon adsorption circuit modelling and cyanide detoxification were used for the project.

• Employing close management and supervision of the metallurgical program conducted at each of the laboratories with timely data review and feedback to allow the program to move forward without delay.

• Involving the metallurgical staff from the selected process engineering firm throughout the metallurgical program. This is essential at a feasibility level of study to ensure that the program fully captures all of the processing parameters required to define the process design criteria and selected process flowsheet.

• Coordinating with geochemists and geotechnical engineers to ensure that process products were obtained during the metallurgical program for specific geochem and geotech evaluations.

The metallurgical program conducted for the Montagne d’Or project served as the basis for defining the process design criteria for a flowsheet that includes: primary crushing, SAG mill grinding, gravity concentration, carbon-in-leach cyanidation with O2 injection, tails thickening and cyanide detoxification based on the SO2/ Air process. An average overall gold recovery of about 94% is projected and includes allowance for losses due to inherent plant inefficiencies. It is worth noting that leach enhancement with O2 injection resulted in reducing the required leach time from 48 hours (with air injection) to less than 30 hours.

Eric Olin:

SRK Latin America